1. Field of the Invention
The present invention relates to an actuator.
2. Description of the Related Art
In recent years, an actuator made from a material of an organic polymer has been developed.
Japanese Patent Application Laid-Open No. 2008-228542 discloses an ion conductive actuator having a three-layer stacked structure in which an intermediate layer is sandwiched by a pair of electrodes. For the intermediate layer, a polymer ion gel (polymer electrolyte) which has a crosslinking structure prepared by polymerizing: a polymerizable ionic liquid monomer which has a cationic moiety or an anionic moiety of an ionic liquid and a polymerizable unsaturated group; and a crosslinking agent containing two or more polymerizable moieties, is used. Use of such a polymer electrolyte enables a whole solid type actuator, and consequently thus formed actuator can prevent a leakage of a liquid and which shows superior practicality compared to an actuator in which a liquid electrolyte is used for the intermediate layer.
In a polymer electrolyte, however, the mobility (ion conductivity) of the electrolyte inevitably decreases, which prevent the whole solid type actuator using the polymer electrolyte for the intermediate layer from obtaining adequate deformation response characteristics. In fact, in an Example of the Japanese Patent Application Laid-Open No. 2008-228542, an actuator is manufactured by using a polymer electrolyte containing a solvent for promoting ion conduction. Further, such a structure has a limitation in practical applications due to a leakage of the liquid. Although a flexible skeleton (such as an ethylene oxide chain) having an ether skeleton structure which has a low free energy of rotation can be introduced into the polymer electrolyte in order to enhance the ion conductivity, it may lead to a case where mechanical characteristics of the obtained polymer electrolyte become poor. When a cationically conductive polymer electrolyte is further used therein as an electrolyte, oxygen of the ether interacts with the cationic species in the electrolyte and causes reduction in the cationic conduction, which may lead to a case where adequate deformation response characteristics cannot be obtained.
In the Examples of Japanese Patent Application Laid-Open No. 2008-228542, only an anionically conductive polymer electrolyte is used. As such, the actuator using the cationically conductive polymer electrolyte has a problem that the deformation response may not be large enough and the actuator shows poor practicality.